title: Increased urinary neutrophil gelatinase associated lipocalin in urinary tract infections and leukocyturia.
abstract: BACKGROUND
  Neutrophil gelatinase associated lipocalin (NGAL) is a protein present in neutrophils. NGAL is a promising biomarker for acute kidney injury. In urinary tract infections, urinary neutrophils can be a potential source of urinary NGAL. We investigated the effects of urinary tract infection and urinary neutrophil counts on urinary NGAL values.
  
  
  METHODS
  NGAL was assayed using an immunoassay (ARCHITECT). Urine flowcytometry was performed with the UF-1000i (Sysmex).
  
  
  RESULTS
  A correlation between the urinary white blood cell (WBC) count and NGAL concentrations was observed: log(Y) (NGAL, μg/L)=1.284+0.439 log(X) (urinary WBC, 10(9) cells/L); r=0.518. Similarly, the bacterial count correlated weakly with NGAL: log(Y) (NGAL, μg/L)=1.796+0.124 log(X) (bacterial count, 10(9) cells/L); r=0.243. Albuminuria correlated moderately with NGAL values: log(Y) (NGAL, μg/L)=1.557+0.339 log(X) (albuminuria, mg/L); r=0.368; α(1)-microglobulin (a1M) correlated weakly with NGAL: log(Y) (NGAL, μg/L)=1.631+0.360 log(X) (a1M, mg/L); r=0.381.
  
  
  CONCLUSIONS
  Leukocyte contributions to urinary NGAL concentrations can be important. In leukocyturia or tubular damage (e.g., intensive care patients), using a fixed cut-off value for interpreting urinary NGAL data can lead to false positive results. Therefore, we suggest a mathematical correction in cases with pyuria (>100×10(9) cells/L) and urinary NGAL concentration >100 μg/L: corrected NGAL (μg/L)=NGAL-0.12 (urinary WBC, 10(9) cells/L).
authors.affiliation: Department of Clinical Chemistry, Ghent University Hospital, Ghent, Belgium.
authors.forename: An-Sofie C
authors.initials: AS
authors.lastname: Decavele
authors.forename: Lien
authors.initials: L
authors.lastname: Dhondt
authors.forename: Marc L
authors.initials: ML
authors.lastname: De Buyzere
authors.forename: Joris R
authors.initials: JR
authors.lastname: Delanghe
mesh_terms: D000209:Acute-Phase Proteins / Q000652:urine*; D000328:Adult; D000368:Aged; D046508:Culture Techniques; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D000071068:Lipocalin-2; D054834:Lipocalins / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011507:Proteinuria / Q000652:urine; D011518:Proto-Oncogene Proteins / Q000652:urine*; D014552:Urinary Tract Infections / Q000097:blood* / Q000382:microbiology / Q000652:urine*
chemical_list: D000209:Acute-Phase Proteins; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D011518:Proto-Oncogene Proteins